Coating for water containing hydraulic cement articles

ABSTRACT

AN ARTICLE CONSTRUCTED OF HYDRAULIC CALCAREOUS CEMENT MATERIAL, SUCH AS PIPE, HAVING A COATING ON ITS WATER CONTAINING SURFACES COMPOSED OF A RESIN COPOLYMER OF VINYL TOLUENCE AND ALPHA METHYL STYRENE TO INHIBIT DISSOLVING AND LEACHING OF WATER SOLUBLE MINERALS FROM THE CEMENTITIOUS MATERIAL, AND A METHOD OF APPLYING THE RESIN COATING COMPRISING THE USE OF THE RESIN DISSOLVED IN PERCHLOROETHYLENE.

United States v Patent 3,676,196 COATING FOR WATER CONTAINING HYDRAULIC CEMENT ARTICLES Stephen Mark Quint, Basking Ridge, and John Junior Dalton, East Whitehouse, N.J., assignors to Johns- Manville Corporation, New York, NY. No Drawing. Filed Nov. 17, 1969, Ser. No. 877,436

Int. Cl- B44d 1/20 US. Cl. 117-96 5 Claims ABSTRACT OF THE DISCLOSURE An article constructed of hydraulic calcareous cement material, such as pipe, having a coating on its water containing surfaces composed of a resin copolymer of vinyl toluene and alpha methyl styreneto inhibit dissolving and leaching of water soluble minerals from the cementitious material, and a method of applying the resin coating comprising the use of the resin dissolved in perchloroethylene.

BACKGROUND INVENTION 7 materials of some soluble forms of lime, such as free or present a decided impediment to the use of these materials in certain applications. The occurrence of water soluble minerals or the extent and rate of leaching thereof is of particular concern with potable water and certain process waters, especially with so-called sof water or water of ing can become critical for reasons well known to water chemists. Typical means of preventing such dissolution and leaching of solubles from cementitious material consists of the application of an asphaltic coating to the surface of the article exposed to the contained water such as pipe or tank interiors. However, in systems of low water transfer or consumption wherein essentially the same volume of water is retained over prolonged periods of contact with the coating, the asphaltic materials often impart an odor or taste to the water.

Additionally, because of the highly porous nature of hydraulic cement materials, including even asbestoscement products formed under substantial pressure, the

application of asphaltic or other water resistant resin coatings dispersed or dissolved in solvent carriers has heretofore required two or more distinct applications to form an effective barrier film since the first application is substantially absorbed into the pores of the structure. A second application, although usually. effective, significantly contributes to manufacturing costs.

SUMMARY OF THE INVENTION 3,676,196 Patented July 11, 1972 ice DESCRIPTION OF THE PREFERRED EMBODIMENT Although this invention is primarily concerned with asbestos-cement water carrying pipe formed with common portland hydraulic cement as the binder phase and therefore is described with reference to such pipe, the problem of dissolution and leaching of lime or water solubles generally from other Water retaining hydraulic cement articles or structures including concrete pipe, tanks, cisterns, reservoir chambers, purification pools, etc., is the same and can be equally elfectively resolved by the herein described means of this invention.

This invention essentially comprises the application of a resin copolymer of vinyl toluene with alpha methyl styrene, for example available on the commercial market as Piccotex from the Pennsylvania Industrial Chemical Corporation, dispersed or dissolved in a solvent consisting of perchloroethylene, to the interior surface of asbestos-cement pipe, or the like exposed surfaces of a water containing article. The quantity of application should range approximately between about 0.2 to 0.5 oz. of the resin solids per square foot of surface area of the cement material, but depending somewhat upon the coarseness of the texture of the surface of the cement body and the degree of porosity thereof. The solution concentration of the resin copolymer in perchloroethylene solvent for optimum application under most conditions should be below mineral content wherein the rate and extent of leachtween approximately 25% e g t) and approximately 40% (weight) of resin solids.

A-common'spray application is preferred because it is of maximum efiiiciency and effectiveness, however other techniques will sufiice such as dipping or brushing.

The agents or means of this invention, viz, the given copolymer dissolved in perchloroethylene solvent, when applied to typical cement material surfaces such as asbestos-cement pipe interiors or ordinary concrete are not significantly absorbed within the interstices or pores of the cementitious material as with waterproofing asphalts o-r resins, but form a tenaciously adhering, water impermeable coating film which is glass-like in appearance, odorless, tasteless, resistant to ultraviolet light and substantially all conditions encountered in a water system, as well as most common chemicals.

A specific illustration of the effects and advantages of this glass-like coating with water carrying asbestos-cement pipe is as follows.

The interior surface of a number of sample sections of asbestos-cement water carrying pipe were spray coated with one application of the resin copolymer of vinyl tolueneand alpha methyl styrene, Piccotex 120 (Pennsylvania Industrial Chemical Corporation) dissolved in perchloroethylene at a concentration of about 30% by weight of resin solids. The spray was applied at a rate of about .5 oz. to 1 oz. solution per square foot of surface area. This single application produced a glass-like inner lining on the surface which was tack-free in about 30 minutes at room temperature, well bonded thereto and of about one to two mils of thickness. Samples of the thus coated asbestos-cement pipe sections were employed in the following evaluations to ascertain their durability and relative inertness of the coating within the environment of their contemplated use.

TABLE 1 Standpipe Test-Distilled Water Retained Unchanged 5 Phenol- Total phthalein Total alkalinity Days pH hardness alkalinity 6. 6 5 l 6. 7 5 0 1O 6. 8 5 0 l5 6. 8 5 0 15 6. 9 5 0 15 6. 8 5 0 l5 TABLE 2 Duration Comments Test Total immersion interior coated 2 weeks.-- No change in lining.

pipe sample in water No flaking.

Fadeometer l Weatherometer Coating integrity and adherence maintained. Outdoor exposure do No change.

Water erosion test (pipe ends 92 hours.. No apparent change plugged and filled to about full in lining. of water, rotated at 55 r.p.m. approximately 1.5 it./min.).

1 Intense ultraviolet light plus heat (extreme acceleration of conditions). 2 Ultraviolet light plus rain (1 day equals approximately 3 days of summer rain and sun).

The performance of the resin in this invention in relation to apparently comparable resinous materials is demonstrated by the following evaluation:

TABLE 3 Resins evaluated Comments Polyterpene Slibject to ultraviolet degradaion. Alpha polyterpene Do. Hydrocarbon Retained solvent odor. Vinyl toluene and alpha methyl Odorless.

styrene eopolymer.

The significance of the solvent in this invention in relation to other common solvents when employed with the vinyl toluene and alpha methyl styrene copolymer is demonstrated by the following comparative evaluation:

TABLE 4 Solvent Comments Odorless mineral spirits- Dries too slowly and retains odor.

Trichloroethylene. Dries too fast.

Xylene Retains odor.

Perchloroethylene Maintains resins on surface of pipe when wet without breaks. Dries resins at efiective rate.

Although a single coating application will sufiice with asbestos-cement products having a smooth surface texture normally attained under proper manufacturing conditions, where the product surface texture is coarse or rough as may occur with worn forming apparatus such as abraded forming mandrels, two applications of the coating material are appropriate to insure an effective barrier film.

The following comprises a specific illustration of the efiects of this invention when the coating is applied in a. two-step procedure wherein the asbestos-cement pipe products present a relatively coarse or rough interior surface attributable to a wear abraded or roughened forming mandrel. V

The interior surfaces of lengths of asbestos-cement pipe were twice sprayed with 30% by weight resin solution of the copolymer of vinyl toluene and alpha methyl styrene dissolved in by weight of perchloroethylene in amount of about 0.2 oz. of resin solids per square foot of surface area with each application, and with the sec ond application following the first at about one half hour. After 48 hours sample sections of the twice coated pipe were tested and produced the following data. That is upon containing the same water for'theindicated periods of time, the given conditions were found:

TABLE 5 Phenol- Total phthalein Total pH hardness alkalinity hardness We claim:

1. A method of inhibiting dissolution and leaching of water soluble minerals from within hydraulic calcareous cementitious material comprising coating the exposed surface of the body of the cementitious material with a solution consisting essentially of resin copolymer of vinyl toluene and alpha methyl styrene dissolved in perchloroethylene followed by drying of the coating.

2. The .method of claim 1 wherein the resin solution is applied in amount of about 0.2 to 0.5 oz. of resin solids per square foot of surface area of the cementitious References Cited UNITED STATES PATENTS 2,285,562 6/ 1942 Britten et al :26033. 8 UA 2,331,263 10/1943 Britton et al. 26033.8 UA 2,973,285 2/1961 Berke'et al. 1'17-123 X 3,106,486 10/1963 Harren et al. 117-123 D 3,294,709-12/1966 Nitzsche et al. 'l 117123 X 3,479,213 11/ 1969' Takeda 260-33.'8 UA OTHER REFERENCES Boandy, Rag H-., Styrene, Its Polymers, Copolymers an Derivatives, -2, 'FP98 S71 05, pp; 12-41-4.

D. MARTIN, Primary Examiner M. R. LUSIGNAN, Assistant Examiner US. Cl. X.R.

l17--123 D, 126 AB 

